Blaser studies the microbiome, which he says "is all the microbes that live in us, that call us home. We are the home of bacteria, and fungi, and protozoa and viruses. Ten percent of the cells in the human body are human and 90 percent are bacterial. So we're nine-tenths bacterial and one-tenth human."

Blaser is interested in the role the microbiome plays in our health. Doctors, he says, have always been interested in what they called the 'natural flora,' but now, thanks to DNA sequencing, we can study the genetic makeup of these microbes.

One of the microbes Blaser has been looking at is Helicobacter pylori (H. pylori), which has been disappearing all over the developed world. As a result, scientists can now measure what the consequences are of having it and not having it.

There now is less stomach cancer and ulcer disease, Blaser said, but scientists have also noticed there are more diseases of the esophagus, like reflux.

There's evidence, Blaser said, that H. pylori is actually protecting the esophagus against reflux. The bacteria's vanishing could be caused by antibiotics, clean water, smaller families, and an increase in Caesarean sections (c-sections).

"We are germophobic," Blaser said. "We forget the world is full of bacteria ... we have to figure out what's the right balance. The idea of killing all of them is a bad idea because we're going to be killing the good guys."